sanctions haven't caused russia to blink. the u.s. accuses moscow of whipping up pro-russian militants who have taken over government buildings in eastern ukraine, a possible prelude to a russian invasion. holly williams is there. >> reporter: in luhansk today, pro-russian separatists seized control of the regional government building. as police looked on, the separatists trampled a ukrainian flag and raised a russian one in its place before moving on to the city's police headquarters, some of them armed with automatic weapons. another uptick in violence in eastern ukraine. the mayor of kharkiv, gennady kernes, is fighting for his life tonight after he was shot in the back in an assassination attempt. and in donetsk, peaceful pro- government demonstrators were attacked by masked-wearing separatists wielding baseball bats and batons. these police officers stood by and did nothing to stop them. as this separatist insurgency gains momentum, ukraine's government and its security forces appear weak and ineffectual. the army's attempt to re